Pen



FIG. 1 is a front perspective view of a pen according to my design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a right side elevational view thereof, the left side elevational view being a mirror image thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof.

The broken lines illustrate unclaimed environmental structure and form no part of the claimed design. 

CLAIM The ornamental design for a pen, as shown and described. 